In a Danish study using observational and genetic data, Näslund-Koch et al found that smoking is observationally associated with a 2.5-fold higher risk for moderate or severe psoriasis. But after using the genetic variant CHRNA3 rs1051730 as a stand-in for high lifelong cumulative smoking, the association was deemed to be only observational, not causal.
Hazard ratios for developing moderate to severe psoriasis were as follows, compared to those without a history of smoking:
- 64 in in ever-smokers with a history of 20 or fewer pack-years
- 23 in ever-smokers with a history of more than 20 pack-years
- 05 per CHRNA3rs10511730 T-allele in ever-smokers.
In addition to these findings, researchers pointed out that smoking is associated with lifestyle and socioeconomic factors that may give rise to comorbidities associated with the development of psoriasis. In concluding their report, which was published in Frontiers in Immunology, the researchers wrote, “Even though we [did] not find a causal association between smoking and moderate to severe psoriasis, smoking restriction and cessation remain important to minimize risk of smoking-related comorbidities.